Low head pumping system for fish farms

Abstract

An impeller pump for moving large volumes of liquid against heads of up to 1 meteris formed by a substantial circular housing having its axis substantially vertical in which an impeller is mounted for rotation on the central axis. The impeller has an maximum diameter substantially equal to the inside diameter of the housing and is formed with a hub and the plurality of blades symmetrically positioned around the hub. Each blade extends radially outward of the hub from a root to a tip and has a foil shaped cross section with a lift to drag ratio at least 75 to 1 at a Reynolds number of under 10 6 . Each of the blades is skewed rearward in the direction of blade rotation so that the apparent aspect ratio of blade is increased and to reduce operating noise. Each blade has an angle of attack of between 2° and 6° and has a rake in the direction of flow through the impeller of between 3° and 7°. The impeller lifts water through the housing and directs it into the fish farm.

We claim: 
     
       1. A pump for moving large volumes of liquid against low heads of up to 1 metercomprising a housing defining a circumferential wall of an annular passage having a central axis, an impeller mounted for rotation on said vertical axis and having a hub portion and plurality of blades symmetrically positioned about said axis, each said blade having a root portion adjacent to the hub and a tip portion at a maximum diameter of said blade adjacent to said circumferential wall of said passage, each of said blades having a substantially elliptical platform shape and having a foil shaped cross section to provide a lift to drag ratio (L/D) of at least 75 to 1 under normal operating conditions when the Reynolds number of flow through the impeller is below 10 6 , each said blade having a center line (CL) skewed rearwardly relative to the direction of rotation of said impeller so that said center line of each blade curves rearward to the direction of rotation of said impeller through a sweep angle α defined by   α=atan(r.sub.r /r.sub.t)     where   r r  is the radius of the root of the blade   r t  is the radius of the tip of the blade and follows a curve defined by     X.sub.i =Cosine θ.sub.i *r.sub.i       Y.sub.i =Sine θ.sub.i *r.sub.i     where     X i  =X coordinate of points i along said center line of the blade in plane view and the X coordinate extends along a radial line extending from the axis of rotation of the impeller through a point of intersection of the center line with the hub   Y i  =Y coordinate of points i along said center line of the blade in plane view and Y coordinate is substantially perpendicular to X   r i  is the radial distance from the point i from the axis of rotation,   θ i  is the angle measured from the X axis at point i and is defined by   θ.sub.I =α(r.sub.i -r.sub.r)/(r.sub.t -r.sub.r)     each said blade having a foil configuration in the NACA4000 series, each said blade at any given radius r i  having a pitch and an angle of attack to provide said lift to drag ratio for said blade.     
     
     
       2. A pump for moving large volumes of liquid as defined in claim 1 wherein each said blade has the same tip radius r t  of between 50 cm and 150 cm. 
     
     
       3. A pump for moving large volumes of liquid as defined in claim 1 wherein each said blade has the same tip radius r t  of between 75 cm and 120 cm. 
     
     
       4. A pump for moving large volumes of liquid as defined in claim 1 wherein each said blade has a pitch angle P in the range of 55° to 65° at the root smoothly converting to a pith angle P of between 12° to 20° at its tip and has a substantially constant angle of attack β of between 3° and 5°. 
     
     
       5. A pump for moving large volumes of liquid as defined in claim 1 wherein said planer form shape will be an ellipse as major axis between 1.3 and 1.7× the maximum radius (r t ). 
     
     
       6. A pump for moving large volumes of liquid as defined in claim 2 wherein said planer form shape will be an ellipse as major axis between 1.3 and 1.7× the maximum radius (r t ). 
     
     
       7. A pump for moving large volumes of liquid as defined in claim 3 wherein said planer form shape will be an ellipse as major axis between 1.3 and 1.7× the maximum radius (r t ). 
     
     
       8. A pump for moving large volumes of liquid as defined in claim 4 wherein said planer form shape will be an ellipse as major axis between 1.3 and 1.7× the maximum radius (r t ) of the impeller, more preferably 1.5 rT . 
     
     
       9. A pump for moving large volumes of liquid as defined in claim 1 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       10. A pump for moving large volumes of liquid as defined in claim 2 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       11. A pump for moving large volumes of liquid as defined in claim 3 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       12. A pump for moving large volumes of liquid as defined in claim 4 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       13. A pump for moving large volumes of liquid as defined in claim 5 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       14. A pump for moving large volumes of liquid as defined in claim 6 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       15. A pump for moving large volumes of liquid as defined in claim 7 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       16. A pump for moving large volumes of liquid as defined in claim 8 wherein each blade has a rake rearward of the direction of fluid flow of between 4° and 6°. 
     
     
       17. A pump for moving large volumes of liquid as defined in claim 1 wherein said central axis is substantially vertical and said housing has a concentric vertical pipe extending thereabove, a float encircling said pipe and positioned to suspend said impeller therebelow. 
     
     
       18. A pump for moving large volumes of liquid as defined in claim 17 wherein said vertical pipe and said housing mount said impeller to permit withdrawal of said impeller by movement substantially vertically through said pipe and said housing. 
     
     
       19. A pump for moving large volumes of liquid as defined in claim 4 wherein said central axis is substantially vertical and said housing has a concentric vertical pipe extending thereabove, a float encircling said pipe and positioned to suspend said impeller therebelow. 
     
     
       20. A pump for moving large volumes of liquid as defined in claim 19 wherein said vertical pipe and said housing mount said impeller to permit withdrawal of said impeller by movement substantially vertically through said pipe and said housing.